1. Field of the Invention
The present invention relates to the treatment of erectile dysfunction, otherwise known as impotence. More specifically, the present invention relates to either a programmable or non-programmable, implantable device for stimulating the cavernous nerve to cause a penile erection.
2. Description of the Prior Art
High incidences of impotence exist in many segments of the adult male population. Impotence has many causes, some of which are psychological and some of which are physiological in origin. Physiologic impotence can be caused by spinal or other injury, disease, or surgical treatments including prostatectomies, cystectomies, abdominal perineal resections, transurethral resections of the prostate, sphincterotomies, and internal urethrotomies.
Impotence is a significant problem. A plethora of urologists and medical product companies have dedicated substantial time and resources to investigate ways to treat impotence. Many of the treatments developed to date have only been marginally successful. Most do not allow for spontaneous sexual relations. Some require the injection of medication to induce an erection. Others require the attachment of external medical devices such as a mechanical vacuum device. Others require that an internal inflatable device be pumped up. Still others result in the near permanent erection of the penis.
More recently there have been various efforts undertaken to treat impotence using electrical stimulation. For example, U.S. Pat. No. 4,585,005 issued Apr. 29, 1986 to Lue et al describes a device for stimulating a penile erection which includes an electrode coupled to a receiver. The electrode is implanted closely adjacent to the cavernous nerve and intermediate the sacral nerves and apex of the prostate. The receiver is also implanted subcutaneously. The system described in the Lue et al patent also includes an external transmitter coupled to an antenna. When the system is used to induce and maintain an erection, the antenna is placed over the receiver so that the antenna can energize the receiver enabling the receiver to transmit electrical energy to the electrode and to the cavernous nerve. A significant disadvantage of the system disclosed in the Lue et al patent is that the external transmitter and antenna must be held in place during coitus.
Another system for treating impotence through electrical stimulation is disclosed in U.S. Pat. No. 5,454,840 granted on Oct. 3, 1995 to Krakovsky et al. This system includes an implantable, programmable electronic pulse generator coupled to an electrode implanted in proximity to the pelvic splanchnic nerve or the pelvic plexus nerve. The system may also include a storage vessel for storage of a vasoactive drug coupled to a thin tube through which the vacoactive drug is carried to the penis. The system is battery powered and includes an infrared remote control transmitter which is operated by the patient or his partner to control the implanted pulse generator.
Disadvantages also exist with the system described in the Krakovsky patent. First, there is no discussion of any techniques to control power consumption and thereby extend battery life. Second, the use of infrared light to actuate the device limits implantation sites for the device. The penetration of infrared light will, of course, be inhibited by the thickness and density of the epidermis, dermis, and any muscle tissue that separates the infrared transmitter from the receiver components of the implanted device. Third, the system described in Krakovsky stimulates the wrong nerves. Stimulation of these nerves may cause erection if enough energy is delivered. However, such energy would cause other body parts to be stimulated as well, resulting in discomfort. Fourth, the amplitude, frequency and pulse widths described in Krakovsky (FIGS. 12-13) present other issues. The low frequencies indicated (1-2 Hz) will not produce the necessary neuro depolarization to provide a complete erection. The combination of 2.50-5 v amplitude and 0.1 second pulse width, delivers energy at levels which are too great. These can result in unintended muscle contractions, pain, and possible necrosis of the stimulated nerves. All of these problems are addressed and resolved by the present invention.